Given the place that politics occupies in the life of most people, their preferences are unlikely ever to cluster at ideological poles.…To us, the essence of polarization is when hot-button issues become salient concerns for a large percentage of people. People feel intensely about these issues because they tap into something deep inside them. It might be the case that people’s preferences are not that different from those of their opponents, but they do not see it that way. When it becomes difficult for people to understand how their adversaries come to have the preferences they do, the political system feels polarized. Even if middle ground is available, people fail to perceive it.
—Marc Hetherington, Jonathan Weiler, Authoritarianism and Polarization in American Politics, (New York: Cambridge University Press, 2009), 24-25.